The present invention relates to a robot controlsystem, and more particularly to a robot control system having a robot controller for transferring control information, control data, etc. through dual-port RAMs between a plurality of CPUs for performing various control functions that are necessary to control operation of an industrial robot, and a teaching box for teaching the robot its operation by processing a command signal entered through an input means with a control means including the CPUs and supplying the processed signal to the robot controller.
Various industrial robots such as welding robots, paint coating robots, assembling robots, or the like are controlled by robot controllers. The robot controllers are required to perform more and more functions to meet recent requirements for more diverse, higher-speed, and more accurate specifications.
For welding a workpiece with a welding robot, for example, the workpiece is positioned on a jig by a clamp, and a welding current is controlled while a welding gun is being moved along a predetermined welding path over the workpiece. During such welding process, various parts of the welding robot are required to operate according to a given procedure, and have to be controlled for a next operation while their operations are being confirmed.
In order to accurately control complex movements of the robot and meet requirements for diversified objects to be controlled, there has been employed a robot control system for controlling a robot with a CPU according to an operation control program. Particularly, a robot control system of parallel distributed processing capability having a plurality of CPUs for carrying out various functions to control a robot is attracting much attention in view of its high cost performance.
In parallel distributed processing systems employing multiple CPUs, the CPUs are interconnected by bus lines. Therefore, the systems require drivers and receivers for sending signals to and receiving signals from the bus lines, and printed-circuit boards supporting the CPUs and their peripherals. Therefore, these parallel distributed processing systems have a large number of hardware parts, and suffer the problems of low processing speeds and low reliability because of a required degree of connection reliability, a bus priority structure for giving the CPUs bus control, and complex control processing operation.
Transfer of control information between the CPUs is effected using a common random-access memory under time-division interrupt control. Consequently, a certain period of time must be consumed for each CPU to effect interrupt processing for saving and restoring data, and the production of a program for such time-division interrupt control is complicated.
To employ a welding robot to carry out a certain welding operation on a workpiece, it is necessary to move a welding gun mounted on the end of a robot arm along a predetermined welding path. The welding path is generally taught as teaching data to the welding robot by a teaching box. In a welding cycle, the welding robot is controlled by a robot controller based on the teaching data. The teaching box for teaching the welding robot its operation has input means for selecting command values for driving axes of the robot and a coordinate system serving as a reference for the teaching process, and setting means for setting operational speeds of the robot. The operator operates these means according to a given procedure to teach the welding robot.
Heretofore, the teaching box is controlled by a CPU in the robot controller, and functions merely as an input unit for the robot controller. In recent years, robots are required to perform an ever increasing number of functions, and hence robots should be taught many operations by their teaching boxes, with the result that the procedure for operating the teaching boxes is quite complex. Accordingly, since more input and setting means are used on teaching boxes, the teaching boxes cannot efficiently be operated, and the processing of signals transferred between the teaching box and the robot controller is complex. Another drawback is that the multifunctions of a robot place an increased burden on its robot controller.